The present invention relates to a data processing device capable of providing an external memory, such as a RAM (Random Access Memory) card, for storing data supported by a built-in power supply and the like, more particularly to a data processing device capable of checking whether the RAM card is employable in the data processing device.
In a data processing device, such as a printer arranged to read character and/or symbol data and print the data on a printing sheet, with a RAM card, it is necessary to check whether the RAM card can be used in the data processing device. Therefore, a RAM card checking operation is executed, when a power supply of the data processing device is turned on, in the following manner.
Some predetermined data are written into particular addresses of the RAM card, the written data are read out, and then the read data are compared with the written data. When the former accords with the latter, it is determined that the storage area is normally used and the card can be used as an external memory.
Recently, a RAM card, with a built-in power supply for electrically supporting the stored data in the RAM card. i.e., so-called back-up power supply, even after the power supply of the data processing device is turned off, or the RAM card is removed from the data processing device, have been used. However, in such a RAM card, when there are download data consisting of dot patterns of characters to be used by an operator, if the checking operation described above is executed, data in the RAM card will be destroyed.